1. Field of the Invention
This invention concerns seismic exploration, in general. More specifically, it deals with a system for testing seismic signal conductors. And, it is particularly applicable to such conductor systems wherein the transducers are very high resistance type, e.g. crystal hydrophones.
2. Description of the Prior Art
In connection with seismic exploration operations, it has been common practice (particularly in land operations) to make use of an ohmeter to test for continuity by switching to the separate geophone circuits in the cables that extend from a recording station of each of the geophone, or transducer, stations. This permitted a rapid continuity check in order to determine whether the geophones were properly connected and/or the cable was not broken. This was quite effective because the resistance of the geophone or geophones was a known quantity, and consequently an open circuit from the causes mentioned (or otherwise) would be quickly indicated. However, in marine seismic operations, the geophones employed are ordinarily crystal hydrophone type instruments and consequently the resistance of these hydrophones is so high that it would indicate the same as an open circuit. Consequently, a continuity check of the type just indicated above, has not been feasible except by making use of individual transformers loated close to the hydrophones. And, a rapid and useful continuity check has not been possible without such transformers. But, by adding a simple unit at each of the geophone stations in accordance with this invention, a continuity check similar to that previously practiced on land seismic operations (with geophones having a normal resistance characteristic) may be carried out.
Thus, it is an object of this invention to provide an improved continuity test system for seismic operations in which very high resistance geophones are employed.